How to restore your iOS device with DFU / Recovery Mode

Sometimes iOS updates go awry. It may happen that the device hangs itself for good, refusing to activate or be recognised by iTunes. In that case, it’s time for a DFU reset, also known as Recovery Mode.

Download an .ipsw file for your device from the Developer Centre (either a beta or the release version) and extract it. Then follow these steps:

turn off your device

open iTunes and have a USB cable handy

while holding the HOME button, insert a USB cable into your device (connected to your computer running iTunes)

the device should turn on and be recognised by iTunes within a few seconds as a device in DFU mode

Option-Click RESTORE in iTunes, then navigate to the .ipsw file of your choice (hopefully the correct one for your device)